Covered elastic strand



June 24, 1930. cl-sHoLM 1,766,776

COVERED ELASTIC STRAND 4 Filed March 22, 1928 2 Sheets-Sheet 1 June 24,1930. L, B. CHISHOLM COVERED ELASTIC STRAND 2 Sheets-Sheet 2 Filed March22, 1928 FEE- Patented June 24, 1930 UNITED STATES LESTER B. CHISHOLM,OF STONEHAM, MA

INC, OF CHELSEA, MASSACHUSETTS,

SSACHUBETTS, ASSIGNOB TO EVERLASTIK, A CORPORATION 01 MASSACHUSETTSCOVERED ELASTIC STRAND Application filed March 22, 1928. Serial No.268,770.

This application is a continuation in part of my application filed April16, 1927, Serial No. 184,341.

The invention relates to an improvement in 5 covered elastic strandsuseful in the making of elastic fabrics. These covered elastic strandscomprise one or more elastic threads forming a core which is coveredwith one or more windings of inelastic fibrous material such as silk orcotton wrapped around the core. The elastic strands glve elasticity orstretchability to the fabric of which they form a part.

One great difliculty in the use of covered elastic strands in fabricsarises when any of the strands become broken. The operation of sewingoften severs or weakens the elastic core of the strand so that when thestrand is placed under tension the broken core will creep and thesevered ends of the core will draw back into the covering causingunsightly puckers to appear and this effect is aggravated because thecore normally lies within the covering under some tension. After theends of the broken core have thus run or contracted, the core will liesubstantially inert and the strand becomes worthless as an elasticmedium. Not only this, but the inelastic thread covering with which theclastic core is provided, no longer being supported at the point of thebreak in the core, will tend to unwind and become loose and unslightly.

Various expedients have been resorted to to 3 obviate this creeping ofthe elastic core with respect to its covering in case the core issevered or broken. Attempt has been made to obviate the difliculty byrunning the covering thread through a bath ofcementing material orelastic adhesive such as latex, and applying the thread thus treated tothe core. Attempt in this direction, however, has been found futile forthe reason that the covering thread is thereby made sticky and-unsightlyand requires one or more finishing thread coverings. Even with suchsecondary covering the result is unsightly, unsatisfactory and uselessfrom a commercial standpoint. The chief difliculty, however, resides inthe fact that the coils or convolutions especially those of the innercoverin or the covering next to .the core become bonded together. Thisacts as an added resistance to the nor- .mal elasticity of the coreuntil such time as repeated stretchings have destroyed the bond betweenthe coils or convolutions and at the same time have incidentallyweakened or ruptured the bond between the elastic core and the coveringthread, thereby permittlng creeping of the core when severed or brokenwhich is the objective difiiculty sought to be overcome. In other words,the cementing together of the coils or convolutions results ultimatelyin destroying the bond between the core and its immediate covering andthis permits creepin of the core in case of breakage.

It is accor ingly the essential object of the invention to produce aproperly durable and attractive covered elastic strand constructed withparticular reference to being readily stretchable, with retained normalelasticity,

and proof against creeping of its elastic core.

with respect to its covering should breakage occur even after longcontinued and repeated stretchings of the strand.

With this object in view, my invention consists in a covered elasticstrand characterized by an elastic core, an inelastic thread covermgapplied to the core, the core lying tensioned within the covering sothat the coils or convolutions of the covering normally abut againsteach other to limit the contraction of the elastic core, and an adhesiveinterposed to form a bond between the core and its thread covering butso excluded from between the abutting surfaces of the respective coilsor convolutions of the covering thread as to prevent their being bondedtogether and enabling them to separate or come together riding upon thecore as the form of the core becomes changed during the flexing orrelaxing of the elastic strand whereby the elastic core is preventedfrom creeping with respect to the covering and whereby also owing to theabsence of the adhesive between the respective abutting coils orconvolutions of the covering thread the elastic strand may be readilystretched without rupturing the bond between the elastic core and itsthread covering. The invention can perhaps best be seen and strand underunderstood by reference to the drawings in which- Figure 1 is a faceview of one of the complete elastic strands constructed in accordancewith the invention, the elastic core belng assumed to be under slightnormal tension.

Fig. 2 is a plan corresponding to Fig. 1, but showing the elastic strandunder greater tension than its normal tension.

Fig. 3 is a transverse sectional view of the strand when tensioned aboveits normal tension.

Fig. 4 is substantially the same as Fig. 1 but in which the strand isshown provided with av secondary thread covering lying outside theprimary covering which is fixed directly to the core;

Fig. 5 is a face view showing the manner in which the inelastic threadcovering is applied to a highly tensioned core, and

Fig. 6 is a side elevation of certain mechanism found useful in themaking of the improved strand and to which mechanism special attentionwill hereinafter be directed.

Referring to the drawings 9- 1 represents the elastic core portion ofthe elastic strand and this may comprise ,one or more elastic threads. 2and 3 represent respectively the inelastic thread coverings of theelastic strand, 2 representing the primary or inner covering in directcontact with the elastic core and 3 the secondary or outer coveringwrapped around the primary covering. Each of these coverings may consistof one or a group of inelastic threads. 4 is the 'cementing materialwhich bonds the primary covering 2 to the elastic core.

. In carrying out the invention the elastic core to be coveredpreliminary to the winding of the covering thereon is tensioned orstretched substantially as shown in Fig. 5 to an extent greater than itsnormal tension or, in other words, the tension under which the core liesin a normal unstretched strand as shown in Fig. 1, it being understoodthat in an elastic strand the core lies within the some tension. Theamount of tension given the core preliminary to the winding of thecovering thereon is preferably to a degree just short of its maximumtension or stretch avoiding all possibility of breakage. To the elasticstrand thus tensioned a thread covering 2 is applied in the usualmanner. This thread covering may consist of a single thread or a numberof combined threads. The thread covering is so applied that a space willseparate its coils. The amount of space between the coils iscommensurate with the amount of stretch desired to be attainedin thecompleted strand. That is, as the core is allowed to contract the coilswill be brought together limiting further contraction of the core whichwill then be held tensioned within the covering and accordingly theamount of separation of the coils determines the amount of stretchdesired to be obtained in the completed strand.

After the application of the thread covering 2 the covered core stilltensioned as aforesaid with the coils of the thread covering separatedfrom one another, is passed through a bath of cementing material inorder that the cementing material may enter between the coils of thethread covering and form a bond between the thread covering and theelastic core, cementing the one to the other. When applied in this way Ihave found that the ordinary rubber cements are inade uate inasmuch asthey will not proper between the coils of the thread and form such bondbetween the its covering as will properly cement the core to thecovering. I have found, however, that if a water-dispersed rubber orwater emulsion of rubber be employed in this connection or one in whichthe rubber is in a very finely divided form, such preparation of rubberwill act effectively and will enter between the coils of the threadcovering and penetrate sufficiently to form a proper bond between theelastic core and the covering.

After passing through the bath of cementing material the covered strandis then freed of surplus cement before the strand has been exposed tothe air. In connection with this freeing of the strand of surpluscement, it is desirable that the covered strand be freed in so far aspossible of all cementing material other than that remaining to form aproper bond between the core and its covering.

After its freeing of surplus cementing material, the covered strand withcore still tensioned has applied to it an outer or secondary threadcovering 3 as shown in Fig.4 care being taken that before theapplication of this outer covering the initially covered strand shallnot contact with any surface on which cementing material mightaccumulate and harden, or, in otherwords, any surface from which bits orpieces of the cementing material might be picked ofl" and adhere to therunning strand. The outer thread covering is applied in the same manner,with substantially the same spacing of coils as the inner covering,except that the spirals are preferably made to runin a reversedirection. This outer covering is for the purpose of adding finish tothe thread and by enveloping the inner covering, bearing more or lesscementing material on its outer surface, prevents it from gummingmechanism or rolls over which the strand is led and to which, were itnot for the outer enveloping covering, cementing material from the innercovering might adhere and accumulate and be picked off in small bits orpieces from time to time by the running strand, it being a verydiflicult matter to eliminate all surplus cementing material from theouter or exposed surface of the initial covercovering core and y entercement may be employed provided the rubber solvent in the rubber cementis not such as will injure the elastic core. After passing through thebath of cementing material the elastic core is freed of surplus cementbefore the core has been exposed to the air the same as before andafterward a thread covering is applied to the elastic core which thenbears a thin film of cementing material, care being taken that beforethe application of the thread covering the coated core shall not contactwith any surface on which the cementing material might accumulate andharden and bits thereof be afterward picked off by the running core. Thethread cover' ing thus applied is applied with coils separated from oneanother according to the manner of application of the initial threadcoverin in the method first described. With the t read covering thusapplied to the elastic core as shown in Fig. 1 a secondary or outerthread covering as shown in Fig. 4 is not necessary. It may be applied,however, if desired to give further finish to the strand.

In Fig. 6 is shown certain mechanism which has been found useful in themaking of the improved strand. As shown in this mechanism -5 and 6represent rotary threadcarrying spools. These spools are arranged invertical alignment one above and spaced from the other, the spool 6being arranged above the spool 5. It will also be observed that thespool 6 is arranged in an inverted position with relation to the spool5. Each of the spools is provided with a flier 7 of a type commonlyemployed in such connection. Located in the space between the two spoolsis a receptacle 8 containing cementing material. At its bottom thisreceptacle is provided with a bottom plate 9 having an opening throughit and this plate is faced on its inner side with a rubber pad 10through which the opening in the plate is continued. At its top thereceptacle is provided with a cover 11 having a relatively large openingthrough it and this opening is closed by a rubber pad 12 having anopening through it which opening is in substantial vertical alignmentwith the opening through the bottom plate andpad at the bottom of thereceptacle. The pad-l2 is held in place by a fixed plate 14 throughwhich the opening through i the pad 12 is continued. In the operation ofthese parts it will be assumed that the elastic core is running undersuitable tension through the spindles of the respective spools andthrough the receptacle and cementing material therein, entering thereceptacle by way of the opening atthe bottom through the bottom plateand pad 10 and passing from the receptacle at the top by way of theopening through the pad 12 and its retaining plate.

The thread covering 2 or the thread which forms the initial covering forthe elastic core, arranged upon the spool 5, is first wrapped around therunning core with the coils of the winding properly spaced from oneanother substantially as shown in Fig. 5. After the initial winding ofthe core the covered core passes upwardly through the openlng in thebottom of the receptacle and pad 10 arranged adjacent it, and thencethrough the bath of cementing material which then becomes applied to thecovered core. As the covered core passes upwardly through the" pad 12and its retaining plate at the top of the receptacle to the atmosphere,the pad 12 will snugly embrace the covered core pass ing through it andacting as a scraper will remove from it all excess cementing materialbefore exposure of the covered core to the atmosphere. After passingfrom the top of the receptacle the covered core passes d1- rectly toreceive the secondary or exterior thread covering 3 which is carried bythe spool 5. No opportunity is given for the running core to havecontact with any surface to which cementing material thereon may adherebefore receiving this secondary thread covering. The secondary threadcovering 3 is wound in substantially the same manner as the primarythread covering 2 with proper spaces between the coils, but preferablyin reverse direction to the primary winding. After the application ofthe outer covering the completed strand passes through the spindle ofthe spool 6 and thence to a suitable takeup mechanism.

Instead of providing the elastic core with an initial thread coveringbefore passing through the bath of cementing material the initialcovering may be dispensed with and the elastic core passed directlythrough the bath of cementing material and afterward receive a threadcovering like that provided by the thread from the spool 6 of themechanism shown, this thread then forming a primary covering. In suchcase a single thread covering only is necessary but another or secondarycovering may be added if desired to give finish just as it is commonlyadded to ordinary covered elastic strands. For a more detaileddescription of the method and apparatus used for the purpose of makingthis improved elastic strand reference is made to ered elastic thread ormy copending application, Serial No. 202;- 906, filed July 1. 1927.

Having thus fully described my invention. I claim and desire to secureby Letters Patent of the United States:-

s a new article of manufacture, a covcord comprising an elastic core, acovering-thread wrapped around the said core, so that its reachesnormally abut against each other to limit the contraction of the saidelastic core, and an adhesive interposed directly between the outersurface of thesaid elastic core and the inner'surface of the saidcovering-thread, but excluded from between the abutting surfaces of therespective reaches thereof, whereby the elastic core is prevented fromcreeping with respect to the covering-thread and whereby, owing to theabsence of adhesive between the respective abutting reaches of the saidcovering-thread, the said elastic core or thread may be readilystretched without rupturing the bond between the said core and. coverinLESTER B. CHISHOLM.

